CN1015486B - Fluid compressor - Google Patents

Abstract

To provide a fluid compressor with a performance in conformity to requirements by constructing it in such a constitution that a piston rotor is fitted in a cylinder in cylindrical form consolidated with a motor rotor within an enclosed chamber, and giving a specific value to the ratio of a working chamber capacity at the end on suction port side to a working chamber capacity at the end on the discharge port side. A motor stator 5 is fitted at the inner wall of an enclosed vessel 2, and a cylinder 3 is concentrically mounted on a motor rotor 4 arranged inside thereof, wherein the two ends are supported rotatably by bearings 6, 7, which are provided with a suction port 8 and a discharge port 10. A piston rotor 11 is fitted in this cylinder 3 eccentrically in an amount (d). This rotor 11 is provided at its periphery with a spiral blade groove 14 which reduces the pitch gradually from the suction toward discharge side, and a spiral blade 15 is fitted in this blade groove 14 in such a way that it can advance and retreat freely. This blade 15 shall be constructed so that the capacity of the working chamber at the end on suction port side is 3-12 times as great as the capacity of working chamber at the end on the discharge port side.

Description

This invention relates to fluid compressors, such as those for compressing refrigerant gas in a refrigeration cycle.

So far, various types of compressors such as reciprocating type and rotary type are known. However, in these compressors, the structure of the driving part and the compression part such as the crankshaft which transmits the rotational force to the compressor part is complicated and the number of parts is large. In addition, in order to improve the compression efficiency of the existing compressor, it is necessary to install a check valve on the output side. However, since the pressure difference on both sides of the check valve is very large, the gas is easy to leak from the check valve. As a result, compression efficiency decreases. In order to solve these problems, it is necessary to improve the dimensional accuracy and assembly accuracy of the parts, which increases the production cost.

U.S. Patent No. 2,401,189 discloses a screw pump having a cylindrical rotating body having an input-side head portion and an output-side head portion. The rotating body is arranged in the hollow shaft and a helical groove is formed on the outer cylindrical surface. At the same time, the helical moldings fitted in the grooves can slide freely. In this way, as the rotating body is driven to rotate, the fluid enclosed in the space between the outer cylindrical surface of the rotating body and the inner cylindrical surface of the hollow shaft and between two adjacent turns of the helical fillet will flow from the hollow shaft to the inner cylindrical surface of the hollow shaft. from one end to the other. That is to say, the above-mentioned screw pump only sends the fluid from one end to the other end, and does not have a mechanism for compressing the fluid.

In addition, in the above-mentioned screw pump, the delivery amount of the fluid is proportional to the pitch of the helical groove and the helical fillet. Therefore, the greater the pitch of the grooves and fillets, the greater the volume of fluid delivered by the pump. But in this case, as the pitch of the slot and fillet increases, the rotation The size of the body and the hollow shaft etc. will also increase, resulting in an overall larger pump.

In view of the above circumstances, an object of the present invention is to provide a fluid compressor with a relatively simple structure, which has a small size and a large capacity while improving its airtightness and compressing fluid efficiently.

In order to achieve the above object, the compressor of the present invention includes: a cylinder having an input side and an output side; a cylindrical rotating body, a part of which is kept in contact with the inner cylindrical surface of the cylinder, and the rotating body can also rotate relative to the above-mentioned cylinder at the same time and is It is arranged eccentrically along the direction of the cylinder axis in the cylinder. There is a helical groove on the outer cylindrical surface of the rotating body. The pitch of the groove is from the input end to the output end of the above-mentioned cylinder; it becomes smaller according to a certain rate of change. , In addition, the above-mentioned groove has an expanding part including a starting point, a changing point and an ending point, and the expanding part includes a first part and a second part, and the first part extends from the starting point to the changing point and its pitch is less than the above-mentioned certain rate of change The rate of change varies, the second part extends from the above-mentioned conversion point to the end point and its pitch changes at a rate of change greater than the above-mentioned certain rate of change; the helical fillet is embedded in the above-mentioned groove, but it can be along the The radial direction of the above-mentioned cylinder slides freely, and at the same time its outer peripheral surface is in close contact with the inner cylindrical surface of the above-mentioned cylinder, and the space between the inner cylindrical surface of the above-mentioned cylinder and the outer cylindrical surface of the rotating body is divided into a plurality of working chambers. The driving part makes the above-mentioned cylinder and the rotating body relatively rotate, and the fluid flowing into the above-mentioned working chamber from the above-mentioned input side is sequentially sent to the working chamber on the output side of the cylinder, and output from the output side of the cylinder to the outside.

In the fluid compressor of the present invention having the above structure, the groove pitch decreases at a constant rate from the input side to the output side of the cylinder. Therefore, the fluid is sent from the input side of the cylinder to the output side through the working chamber, and the fluid can be compressed efficiently without using a check valve or the like.

In addition, the above-mentioned groove has an expanding portion, so the pitch of the groove decreases at a certain rate of change. Compared with smaller compressors, the discharge volume of fluid can be increased. Thus, a large-capacity compressor can be realized without increasing the volume of the device.

Fig. 1 shows an embodiment of fluid compressor of the present invention to Fig. 10D:

Figure 1 is a sectional view of the overall compressor;

Fig. 2 is the side view of rotating body;

Figure 3 is a side view of the fillet;

Fig. 4 is the sectional view of the compressing part of above-mentioned compressor;

Fig. 5 is a sectional view along the line V-V in Fig. 4;

Fig. 6 is the plan view of the above-mentioned rotating body for illustrating the shape of spiral groove;

Fig. 7 is the side view of above-mentioned rotating body, wherein a part is section;

Fig. 8 has shown the relation of above-mentioned helical groove and working chamber volume;

9A to 9C are respectively enlarged plan views of different parts of the above-mentioned spiral groove;

10A to 10D are the compression process of the refrigerant gas;

11A to 11D are respectively sectional views showing the relative positions of the cylinder and the rotating body in the above-mentioned compression stroke;

Figure 12 has shown the relationship between the volume of the spiral groove and the working chamber about the modified embodiment;

13 and 14 are a plan view and a side view of the rotary rod concerning this modified embodiment.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 shows an embodiment illustrating the application of the present invention to a hermetic compressor for compressing a refrigerant in a refrigerating cycle.

The compressor includes a hermetic casing 10 , a motor portion 12 and a compression portion 14 disposed within the casing. The motor part 12 includes approximately An annular stator 16 and an annular rotor 18 provided inside the stator.

As shown in Figures 1 and 4, the compression section 14 has a cylinder 20, on the outer cylindrical surface of which the rotor 18 is fixed coaxially. The two ends of the cylinder 20 are respectively supported by bearings 22a and 22b fixed inside the casing 10, which can rotate freely and are airtight at the same time. In particular, the right end of the cylinder 20, the input side, is fitted into the outer cylindrical portion of the bearing 22a and is rotatable, and the left end of the cylinder, the output side, is fitted into the outer cylindrical portion of the bearing 22b and is rotatable. Accordingly, the cylinder 20 and the rotor 18 fixed thereto are supported coaxially with the stator 16 through the bearings 22a and 22b.

A cylindrical rotary rod 24 having a diameter smaller than the inner diameter of the cylinder is provided in the axial direction in the cylinder 20 . The central axis A of the rod 24 is arranged eccentrically with respect to the central axis B of the cylinder 20 by an offset e, while a part of its outer cylindrical surface remains in contact with the inner cylindrical surface of the cylinder. Thus, both ends of the rotating rod 24 are rotatably supported by the bearings 22a and 22b, respectively.

As shown in Figures 1 and 4, a fitting groove 26 is formed on the outer cylindrical surface of the end of the input side of the rotary rod 24, and the driving pin 28 protruding from the inner cylindrical surface of the cylinder 20 can move forward and backward freely along the radial direction of the cylinder. Insert it into the mating groove. Therefore, when the motor part 12 is energized to rotate the cylinder 20 together with the rotor 18, the rotational force of the cylinder is transmitted to the rotating rod 24 through the pin 28, and as a result, a part of the rod 24 is held in contact with the inner cylindrical surface of the cylinder 20 in the cylinder. Turn inside.

As shown in FIGS. 1 and 2 , a helical groove 30 extending between both ends of the rod is formed on the outer cylindrical surface of the rotating rod 24 . Moreover, as shown in FIG. 2, except for the expansion part which will be mentioned later, the pitch of the groove 30 gradually changes at a certain rate from the right end to the left end of the cylinder 20, that is, from the input side to the output side of the cylinder. become smaller. The number of turns of the groove 30 is preferably 4 to 7 turns, and 4 turns are used in this embodiment.

A helical molding 32 shown in FIG. 3 is fitted into this groove 30 . The fillet 32 is made of elastic material such as "Dongfulong" (trademark), and is screwed into the groove 30 by using the elasticity. The thickness t of the fillet 32 approximately corresponds to the width of the groove 30 . Therefore, each part of the molding is elastically deformed along the shape of the groove 30 and can freely advance and retreat relative to the groove 30 along the radial direction of the rotating rod 24 . In addition, the outer cylindrical surface of the fillet 32 and the inner cylindrical surface of the cylinder 20 slide closely against the inner cylindrical surface of the cylinder.

Thus, as shown in FIGS. 1 and 4 , the space between the inner cylindrical surface of the cylinder 20 and the outer cylindrical surface of the rod 24 is divided into a plurality of working chambers 34 by the fillet 32 . Each working chamber 34 is defined by adjacent two circles of the fillet 32, as shown in Figure 5, along the fillet, extends from the contact portion of the rod 24 and the inner cylindrical surface of the cylinder 20 to the contact portion of the next circle of fillet , thus forming a shape roughly in the shape of a bud in early March. On the other hand, the volume of the working chamber 34 gradually decreases from the input side to the output side of the cylinder 20 .

As shown in FIGS. 1 and 4 , in the bearing 22 a supporting the input side of the cylinder 20 , a suction hole 36 is formed to penetrate in the axial direction of the cylinder 20 . One end of the suction hole is opened in the input side of the cylinder 20, and the other end is connected to the suction pipe 38 of the refrigerating cycle. Further, in the bearing 22b supporting the output side portion of the cylinder 20, a discharge hole 40 extending in the axial direction of the cylinder 20 is formed. One end of the discharge hole 40 is opened in the output side of the cylinder 20 , and the other end is opened in the inside of the housing 10 . The discharge hole 40 may also be opened on the cylinder 20 . In addition, a pressure introduction passage 42 is formed inside the rod 24, extending from the left end of the rod to near the right end. The left end of the passage 42 communicates with the inside of the casing 10, more precisely, the bottom thereof, through a passage 44 formed on the bearing 22b. The opening of the right end of the passage 42 is formed at the bottom of the groove 30 on the rotary rod 24, and the bottom of the housing 10 stores the lubricating oil 41. Therefore, when the pressure inside the housing 10 rises, the lubricating oil 41 enters the space between the bottom of the groove 30 and the fillet 32 through the passages 44 and 42 .

Reference numeral 46 in FIG. 1 denotes a discharge pipe communicating with the inside of the casing 10 .

Next, the shape of the spiral groove 30 and the working chamber 34 will be described in detail.

As shown in FIG. 6 , the helical groove 30 extends from the right end to the left end of the rotating rod 24 and has four turns in total. Thus, three working chambers 34 a , 34 b and 34 c are defined by the molding 32 fitted into the groove 30 . A dotted line C in FIG. 6 indicates a contact position of the outer cylindrical surface of the rotary rod 24 with the inner cylindrical surface of the cylinder 20 . Thus, the working chambers 34a to 34c are separated by lines C1, C2, C3 and C4, respectively.

As shown in FIG. 8, the groove 30 is shaped such that the volumes of the working chambers 34a to 34c gradually decrease. The vertical axis in FIG. 8 represents the distance from the right end of the rotating rod 24 to the groove 30 along the axial direction of the rotating rod 24, and the horizontal axis represents the phase of the groove 30 advancing along the outer cylindrical surface of the rotating rod. In addition, the lines A and B in FIG. 8 show the changing state of the pitch of the groove 30, and the phase of the line B is shifted by 360° with respect to the line A. The hatched parts in Fig. 6 and Fig. 8 represent the areas of the working chambers 34 respectively, and the above-mentioned hatched parts are regarded as the volumes of the working chambers in the following description.

As shown in FIGS. 6 and 8 , except for the first turn, the pitch of the groove 30 decreases at a certain rate of change from the input side to the output side of the cylinder 20 . The first turn of the groove 30 forms the expansion portion 50 of the present invention. The expanding part 50 has a start point 50a that coincides with the start point of the first turn, an end point 50b that coincides with the end point of the first turn, and a transition point 50c located between the start point and the end point. The pitch of the first part 52a extending from the starting point 50a to the transition point 50C decreases with a rate of change less than the above-mentioned certain rate of change; and the pitch of the second part 52b extending from the transition point 50C to the end point 50b is greater than the above-mentioned certain change rate. The rate of change increases. In addition, in FIGS. 6 and 8 , the two-dot chain line 54 indicates the first turn of the groove when the groove 30 changes at the above-mentioned constant rate of change from the beginning to the end. From these figures, it can be known that since the groove 30 has an expanded portion, compared with the case where the pitch of the groove 30 decreases at a certain rate of change from the beginning to the end of the groove, the first pitch can be reduced. The volume of the working chamber 34 a is enlarged by a portion of the volume of the area 56 surrounded by the wire 54 and the expansion part 50 .

If the volume of the first working chamber 34a is expressed as Vi and the volume of the third working chamber 34c is expressed as Vo, the compression ratio of the compressor is determined by the volume ratio Vo/Vi. In addition, when the compressor is placed in a refrigerating cycle, it is required that the suction pressure of the refrigerant gas at the suction port 36 and the discharge pressure of the refrigerant gas at the discharge port 40 be set within a certain range. That is, if pi represents the suction pressure and Po represents the discharge pressure, the pressure ratio Po/Pi is required to be set at 3-12 corresponding to the type of refrigerant gas and the type of refrigeration cycle. Therefore, in order to obtain a desired pressure ratio Po/Pi, it is necessary to make the compression rate of the compressor match the pressure ratio. For this reason, the volume ratio Vo/Vi of the working chambers 34a and 34c should be 3-12.

As shown in FIGS. 6 and 7, an introduction groove 60 is formed on the outer cylindrical surface of the rotating rod 24, and the groove 60 extends from the input side to the output side of the rod in the axial direction of the rod. The introduction groove 60 is deeper than the groove 30 and extends from the lower surface of the molding 32 . The refrigerant gas sucked into the cylinder 20 is introduced into the first working chamber 34 a through the introduction groove 60 . Therefore, when the rotation direction of the rotation rod 24 is R, the start end of the first working chamber 34 a is defined by the end edge 60 a of the introduction groove 60 . Therefore, the volume of the working chamber 34a can be set arbitrarily by adjusting the formation position of the introduction groove 60 . In addition, the volumes of the working chambers 34a and 34b are basically determined when designing the compressor according to the pitch of the groove 30, but as described above, adjusting the formation position of the introduction groove 60 and then adjusting the volume of the first working chamber 34a can correspond to The volume ratio Vo/Vi of the working chamber is set to a constant value for the pressure ratio Po/Pi required for the refrigeration cycle.

The pitch of the helical groove 30 becomes smaller from the input side to the output side of the cylinder 20 . In this case, the inclination angle, that is, the helix angle β of the portion of the grooves on the input side shown in FIG. 9B is larger than the helix angle of the portion of the grooves 30 on the output side shown in FIG. 9A . Therefore, in order for the molding 32 to move in the radial direction of the rotary rod 24 in the groove 30 on the input side, the amount of deformation of the molding needs to be increased. When the amount of deformation increases, the friction between the groove 30 and the molding 32 also increases, and as a result, smooth movement of the molding is prevented. Then, a gap is generated between the molding 32 and the cylinder 20 to cause air leakage. In addition, as shown in Figure 9c, even if the lead angle β of the groove 30 is the same, when the depth _l2 of the groove is larger than the depth _l1 of the groove shown in Figure 9B, the amount of deformation of the fillet 32 will be further increased . It is therefore easier to cause poor movement of the molding 32 .

According to the invention, the groove 30 is formed such that the angle of rise of the groove 30 increases the gap between the groove 30 and the fillet 32 as the depth increases. Therefore, even if it is located on the input side of the cylinder 20, the malfunction of the molding 32 can be reduced. In addition, the lift angle β of the groove 30 is larger on the input side of the cylinder 20, that is, on the low-pressure side, and gas leakage can be prevented by appropriately selecting the above-mentioned clearance.

Next, the operation of the compressor configured as above will be described.

First, when the motor portion 12 is energized, the rotor 18 rotates, and the cylinder 20 integral therewith also rotates. Simultaneously, the rotary rod 24 is also driven to rotate in a state where a part of its outer cylindrical surface is in contact with the inner cylindrical surface of the cylinder 20 . The relative rotational movement of the rotary rod 24 and the cylinder 20 is ensured by the limiting means formed by the pin 28 and the matching groove 26 . The molding 32 thus also rotates integrally with the rotating rod 24 .

Since the fillet 32 rotates with its outer cylindrical surface in contact with the inner cylindrical surface of the cylinder 20, each part of the fillet 32 is pulled when approaching the contact portion of the outer cylindrical surface of the rotating rod 24 and the inner cylindrical surface of the cylinder 20. Pressed into the groove 30, and moves outward from the groove when leaving the contact portion. On the other hand, when the compression part 14 operates, refrigerant gas is sucked into the cylinder 20 through the suction pipe 38 and the suction hole 36 . The gas is introduced through the slot 60 , is firstly enclosed in the first working chamber 34a located on the input side closest to the cylinder 20 . Then, as shown in Fig. 10A to Fig. 10D, with the rotation of the rotating rod 24, the above-mentioned gas is sequentially sent to the second and third working chambers 34b and 34c. Then, since the volume of the working chamber 34 gradually decreases from the input side to the output side of the cylinder 20, the refrigerant gas is gradually compressed when being sent to the output side. The compressed refrigerant gas is then discharged from the discharge hole 40 formed in the bearing 22 into the casing 10, and then returned to the refrigeration cycle through the discharge pipe 46. In addition, in the process of the above-mentioned compression operation, changes in the relative positions of the cylinder 20 and the rotary rod 24 are as shown in FIGS. 11A to 11D .

In the compressor configured as described above, the pitch of the groove 30 formed in the rotary rod 24 gradually decreases from the input side to the output side of the cylinder 20 . That is, the volume of the working chamber 34 partitioned by the fillet 32 gradually decreases toward the output side. Therefore, the refrigerant gas can be compressed during the process of conveying the refrigerant gas from the input side to the output side of the cylinder 20 through the working chamber 34 . In addition, since the refrigerant gas is conveyed and compressed in a state sealed in the working chamber 34, the gas can be compressed efficiently without providing a discharge valve on the output side of the compressor.

The omission of the discharge valve can simplify the structure of the compressor and reduce the number of components. In addition, since the rotor 18 of the motor section 12 is supported by the cylinder 20 of the compression section 14, there is no need to provide a rotating shaft and bearings dedicated to supporting the rotor. Therefore, it is possible to further simplify the structure of the compressor and reduce the number of parts.

The cylinder 20 and the rotary rod 24 contact each other while rotating in the same direction. Therefore, the friction between the materials of its parts is small, and each can rotate smoothly, with the result that vibration and noise are also small.

The delivery capacity of the compressor is determined by the initial pitch of the fillet 32, which is located in the cylinder The volume of the first working chamber 34a on the input end side of 20 is determined. The first turn of the helical groove 30 of the present embodiment constitutes the expansion portion 50, and compared with the situation where the pitch of the groove 30 decreases at a certain rate of change from the beginning to the end of the groove, the volume of the first working chamber 34a can also be increased. That is, the discharge volume increases. Therefore, the discharge capacity can be set larger than that of other compressors in which the total length of the rotary rod and the helical groove and the number of turns of the groove are equal. As a result, a large-capacity compressor can be obtained without increasing the volume of the device, and the capacity of the refrigeration cycle can be improved.

In addition, the compression ratio of the compressor, that is, the volume ratio Vo/Vi of the first working chamber 34a and the second working chamber 34c, can be set corresponding to the range of the pressure ratio Po/Pi required by the compressor to be placed in the refrigeration cycle. In the range of 3 to 12, in particular, it can be set to the same value as the required pressure ratio. For this reason, the refrigerant gas compressed by the compressor and discharged into the refrigerating cycle is smoothly discharged with almost no change in pressure. That is, it is possible to compress refrigerant gas with a compression capacity suitable for a refrigeration cycle without generating overcompression and undercompression. Therefore, the compression capacity of the compressor can be freely changed within a certain range by changing the formation position of the introduction groove 60 of the rotary rod 24, that is, by changing the volume of the first working chamber 34a. Therefore, in the manufacture and assembly of the compressor, it is possible to easily meet the design requirements (performance requirements) for the compression capacity of the compressor in the refrigeration cycle. Thereby, it is possible to provide a compressor having capability variability that is not available in conventional compressors.

In addition, the fillet 32 of the compressor has 4 turns, at least two working chambers can be formed, and three working chambers are formed in the embodiment. Also, since the volumes of these working chambers 34a to 34c are gradually reduced, the refrigerant gas is gradually compressed while passing through these working chambers. Thus, to complete one compression stroke, the rotary rod 24 and cylinder 20 must rotate three times. In this way, it is generally made into three working chambers. Due to the extended pressure The stroke is shortened, so that the pressure difference of the refrigerant gas in adjacent working chambers can be relatively small and the pressure change acting on the fillet 32 can be small. In addition, when the rotating rod 24 and the cylinder 20 make one revolution, the load on the motor part 12 can also be reduced accordingly.

On the contrary, when the number of turns of the fillet 32 is less than 4, for example 3, there are at most two working chambers, and in some cases there is only one. In this case, the pressure difference between the working chambers becomes larger, and the pressure acting on the molding also changes greatly. Therefore, pressure is concentrated on a part of the fillet to deform the fillet, and this deformation of the fillet becomes a cause of refrigerant gas leakage. Furthermore, it is necessary to complete a compression stroke with one or two revolutions of the rotating rod and cylinder, which increases the load on the motor part. For this purpose, a large motor section is necessary.

According to this embodiment, compared with the case of 3 turns or less, the above-mentioned fillet can smoothly compress the refrigeration gas without causing a large pressure change, and as a result, the occurrence of gas leakage can be reduced. At the same time, the drive torque required by the motor section 12 can be reduced, and compression can be performed efficiently with a small motor. Furthermore, the life of the molding can be extended because the pressure applied to the molding is small.

In addition, the number of turns of the fillet 32 is not limited to 4 turns, and the same advantages as those of the above-mentioned embodiment can also be obtained if there are more than 5 turns. However, a sufficient effect can be obtained when the number of working chambers is 5, and if the number of working chambers exceeds this number, the friction loss between the molding 32 and the groove 30 will increase. For this reason, as the driving torque required by the electric motor portion 12 increases, it cannot be expected to increase the compression efficiency. In other words, if the number of turns of the fillet exceeds 7, the above-mentioned undesirable phenomenon will occur. Therefore, it can be seen that in order to reduce the size and weight of the compressor as much as possible and improve the compression efficiency, it is obvious that the number of turns of the fillet 32 is 4 to 7 most suitable.

In addition, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

For example, as shown in FIG. 12, a part of the helical groove 30 may be formed as an equal-pitch portion 62. These equal-pitch portions 62 form a certain inclination with respect to the axis of the rotary rod 24 . Thus, the equal-pitch portion 62 can be used to adjust the degree of pressure change of the refrigerant gas compressed in the working chamber.

In addition, in the above-mentioned embodiment, the expanded portion 50 of the groove 30 is provided in the first turn of the groove, but the overall length of the expanded portion may be longer or smaller than the overall length of the first turn. Thus, by adjusting the overall length of the expansion portion 50, the compression capacity of the compressor can be easily adjusted.

As shown in FIGS. 13 and 14 , the introduction hole 64 may be used instead of the introduction groove for introducing the refrigerant gas into the first working chamber 34 a. The introduction hole 64 is formed in the rotating rod 24 along the rotating rod axial direction, and has an introducing port 64a opened on the input side end surface of the rotating rod and an outlet port 64b formed on the outer cylindrical surface of the rotating rod. Then, the starting end of the first working chamber 34 a is defined by the end edge of the outlet 64 b located on the upstream side in the rotation direction R of the rotation rod 24 . Even in such a structure, as in the above-mentioned embodiment, the volume of the first working chamber, that is, the discharge volume of the compressor can be adjusted by adjusting the opening position of the outlet port 64b.

In addition, the compressor of the present invention is not limited to use in a refrigeration cycle, and can be applied to other applications.

Claims (9)

1. A fluid compressor, which consists of the following parts: a closed casing (10), a cylinder (20) that is located in the closed casing, one end of which is the input side and the other end is the output side, and is located in the cylinder along the cylinder Axially, and a part of it keeps in contact with the inner cylindrical surface of the cylinder, eccentrically arranged, a cylindrical rotating body (24) that can rotate, on the outer cylindrical surface of the rotating body, there is a A plurality of circles including the first circle, and the helical groove (30) whose pitch gradually decreases at a certain rate of change from the input side to the output side of the cylinder has an outer surface that is in close contact with the inner cylindrical surface of the cylinder, embedded in the helical groove and can move toward the radial direction of the rotating body, and divide the space between the inner cylindrical surface of the cylinder and the outer cylindrical surface of the rotating shaft body into a plurality of helical fillets (32) of working chambers, And the driving part (12) that makes the cylinder and the rotating body rotate relatively, it is characterized in that: the said helical groove has an expansion part (50) including a starting point, a transition point and an end point, and the starting point of the expanding part is the same as the first circle of the above-mentioned helical groove The expansion part includes the first part (52a) stretching from the starting point to the transformation point, whose pitch changes at a rate of change less than the above-mentioned certain rate of change, and the first part (52a) extending from the transformation point to the end point, whose pitch is greater than the above-mentioned certain rate of change. The rate of change is the rate of change for the second portion of the change (52b). 2. A compressor according to claim 1, wherein the end point of said expansion portion coincides with the end point of said first turn. 3. The compressor of claim 1, wherein said helical groove has at least four turns defining at least two working chambers. 4. A compressor according to claim 3, wherein the number of turns of said helical groove is in the range of 4-7. 5. The compressor according to claim 1, wherein said helical groove has an equal-pitch portion with a constant pitch, and said equal-pitch portion is closer to the output side of said cylinder than said expansion portion. 6. The compressor according to claim 1, wherein said working chamber includes a first working chamber located on the input side of the cylinder and a final working chamber located on the output side of the cylinder, and the volume of the first working chamber is the final working chamber. 3 to 12 times the volume. 7. The compressor according to claim 6, wherein said rotary body has an introduction groove formed on its outer cylindrical surface for introducing the fluid introduced from the input end of said cylinder into said first working chamber, and said introduction groove One end is open at the cylinder input side end surface of the rotary rod, and the other end edge extends along the axis of the rotary rod and defines the input side boundary of the first working chamber. 8. The compressor according to claim 6, wherein said rotary body has an introduction hole for introducing fluid introduced from the input end of said cylinder into said first working chamber, and said introduction hole has a cylinder input side opening to said rotary rod. The inlet on the end surface of the shaft and the outlet opening on the outer cylindrical surface of the above-mentioned rotating rod and defining the input-side boundary of the first working chamber. 9. The compressor of claim 1, wherein said fillet is embedded in said helical groove with a gap, said gap decreasing as the pitch of said groove decreases.

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